Segmentation Fault with VECs when multithreaded

[sestephens73]

In the QR-factorization example, we spawn multiple threads for calling into VECs. Each VEC then calls into its own NumPy thread pool to do a qr factorization on its block. A segmentation fault occurs during this process. It's more likely to happen when more threads calling VECs are used.

Parla.py/examples/qr_factorization/vec-segfault.py

Lines 45 to 63 in 991f036

	def VEC_qr(A):
	# Acquire lock
	VEC_id = VEC_q.get()
	mystring = ['|' for x in range(MAX_WORKERS)]
	mystring[VEC_id] = 'x'
	print(mystring)
	with VECs[VEC_id]:
	Q, R = np.linalg.qr(fixarr(A))
	mystring = ['|' for x in range(MAX_WORKERS)]
	mystring[VEC_id] = 'o'
	print(mystring)
	# Release Lock
	VEC_q.task_done()
	VEC_q.put(VEC_id)
	return Q, R

[insertinterestingnamehere]

Probably related: #68

[insertinterestingnamehere]

Probably also related: #61.